1. Field of the Invention
The present invention relates to an electrophotographic toner useful for developing an electrostatic latent image, a toner container containing the toner, an image forming apparatus using the toner container and a method for supplying the toner from the toner container.
2. Discussion of the Related Art
Now is the age of information, and therefore a huge amount of copies are reproduced using electrophotographic copiers. At the present day, various electrophotographic image forming apparatus are known. The image forming apparatus typically include an image bearing member, a charging device, a light irradiating device, a developing device, an image transfer device, a fixing device, a cleaning device, etc. Images are typically formed by the following method:
(1) the charging device charges the entire surface of the image bearing member (i.e., a photoreceptor);
(2) the light irradiating device irradiates the image bearing member with imagewise light to form an electrostatic latent image on the image bearing member;
(3) the developing device develops the latent image with an electrophotographic toner to form a toner image on the image bearing member;
(4) the image transfer device transfers the toner image from the image bearing member to a receiving material;
(5) the fixing device fixes the toner image upon application of heat or pressure, or combination thereof, to produce a document having a fixed image thereon; and
(6) the cleaning device removes the toner remaining on the image bearing member even after the toner image is transferred on the receiving material, to prepare for the next image forming operation.
The toner is included in a toner container, and is supplied to the developing area in the developing device. There are two types of toner containers, one of which is a vertical type container and another of which is a horizontal type container. The vertical type container is suitable for supplying a toner to the developing area at a time by reversing the toner container.
The horizontal type container is suitable for gradually supplying a toner to the developing area. Several types of horizontal type containers are known. Japanese Laid-Open Patent Publication No. 7-20705 discloses a horizontal type cylindrical toner container which has spiral guide grooves on the internal surface thereof. This toner container is gradually rotated to supply the toner therein to the developing area.
Recently, the horizontal type toner containers are frequently used for image forming apparatus such as copiers, printers and facsimile machines. However, the horizontal type toner containers have a relatively poor toner discharging ability compared to the vertical type toner containers.
In addition, recently a need for clear images increases more and more. Therefore toners having a high level of function, such as the following toners, are developed and practically used.
(1) toners having a relatively small particle diameter;
(2) toners which do not include an oil;
(3) toners having a spherical shape; and
(4) polymerized toners which are prepared by a polymerization method.
These high functional toners generally have a poor fluidity (i.e., a poor discharging ability) although the reason is not known yet. Therefore, these toners tend to remain in the toner containers without being supplied after image forming operations are repeated for a long time.
In addition, these high function toners tend to form the aggregate in which toner particles adhere to each other. When aggregates are formed in a toner, the discharging ability of the toner deteriorates.
These drawbacks of the horizontal toner containers have not been recognized to be solved. Therefore, the solution has not been proposed yet.
Accordingly, an object of the present invention is to provide a toner having a good discharging ability, i.e., to provide a toner which can be supplied to a developing area in a proper amount (not too little and not too much).
Another object of the present invention is to provide a toner container having a good toner discharging ability.
Yet another object of the present invention is to provide an image forming apparatus provided with a toner container having a good toner discharging ability.
Still another object of the present invention is to provide a method for almost completely supplying a toner contained in a toner container.
To achieve such objects, the present invention contemplates the provision of a toner having a volume average particle diameter not less than 6.0 xcexcm, and a number average particle diameter, and a particle diameter distribution such that toner particles having a particle diameter not greater than one half of the number average particle diameter of the toner are present in the toner in an amount of not greater than 10% by number, and toner particles having a particle diameter not less than 1.5 times the volume average particle diameter of the toner are present in the toner in an amount of not greater than 15% by volume.
The toner preferably has a one-particle adhesion force not greater than 3.0 dyne/contact.
In another aspect of the present invention, a cylindrical toner container is provided which includes at least an opening, and a spiral guide groove formed on the internal surface thereof and which is used for containing the toner mentioned above and for an image forming apparatus having a toner supplying device including a container supporting member and a toner container rotating member which rotates a toner container.
It is preferable for the toner container to be provided in the image forming apparatus so as to be easily put on or taken off the image forming apparatus.
In yet another aspect of the present invention, an image forming apparatus including a developing device, and a toner supplying device including a container supporting member and a toner container rotating member which rotates the toner container containing the toner mentioned above.
In still another aspect of the present invention, a method for supplying a toner to a developing area of the image forming apparatus mentioned above which includes providing the toner container including the toner mentioned above, setting the toner container in the image forming apparatus, supplying the toner to the developing area of an image forming apparatus while rotating the toner container.
These and other objects, features and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.